(1) Field of the Invention
The present invention relates to a method of fabricating a metal-insulator-metal capacitor, and more particularly, to a method of forming a metal-insulator-metal capacitor without metal corner erosion in the fabrication of an integrated circuit device.
(2) Description of the Prior Art
Capacitor matching for metal-insulator-metal (MIM) capacitors in RF mixed signal applications is increasingly critical owing to stringent requirements. Nevertheless, process-instigated issues present major obstacles to efficient capacitor matching. One major process-instigated issue is varying capacitor characteristics owing to different extents of top metal erosion during bottom metal electrode patterning. The size of the landing area for a contact array, especially around the metal corners can differ between MIM capacitors. Because of relatively poor etch selectivity between photoresist and metal, and because of thinner resist thickness lining the top metal electrode, especially along the sidewalls and top edges, the corners of the top metal electrode will be aggressively etched. This results in jagged edges at the top metal or corner rounding of the top metal electrode. The degree of etching or rounding differs from capacitor to capacitor and is uncontrollable. This makes capacitor matching for MIM in mixed signal applications difficult. It is desired to find a method to eliminate top metal corner shaping and also to attain better etch process control.
Co-pending U.S. patent application Ser. No. 09/726,655 to Cha et al, filed on Nov. 30, 2000, teaches another method to eliminate top metal corner shaping by forming spacers on the top metal electrode. The spacers provide a sloping contour for the photoresist so that photoresist thinning at the corners is avoided. U.S. Pat. No. 5,812,364 to Oku et al, 5,998,264 to Wu, 5,466,617 to Shannon, and 5,162,258 to Lemnios et al show various MIM capacitor processes.